Public and commercial map databases are frequently very large and awkward to use, particularly in portable applications. Not only do such databases frequently require excessively large and expensive storage, access to data within such databases is frequently very slow. When data is transferred and/or stored to, for example, a computer hard drive with a large amount of available memory capacity, data compression may not be critical because the computer's hard drive can accommodate data files that are quite large. However, when data files are transmitted over low speed systems, or systems that operate with a low bandwidth, data compression becomes important. Similarly, when data is recorded, transferred, and/or stored to a device in which storage space is highly restricted or expensive, such as a personal digital assistant, a pager, or a cellular telephone, data compression is a primary factor. For these applications and others, a more efficient data compression method is particularly critical. Therefore, a method to reduce or compress a very large database down to a manageable and economical size while preserving accuracy is required. Similarly, a method to quickly retrieve, decompress, and display data is required. The methods taught herein address fast and virtually loss-less data compression. A file system taught herein speeds location and display of map information. Data is quickly decompressed and presented to an user via a CRT or other type of display. Efficient panning and zooming taught herein speed screen refreshing for smooth display. Novel memory management reduces system resource requirements while providing crisp display updates.